Increased taxes are extremely unpopular. Gas taxes, which are supposed to fund road maintenance, are almost always a fixed per-gallon amount, so they gradually

Increased taxes are extremely unpopular. Gas taxes, which are supposed to fund road maintenance, are almost always a fixed per-gallon amount, so they gradually erode due to inflation. They also effectively shrink due to increasing fuel efficiency. Just keeping gas taxes actually steady looks like an increase, and voting for that is a good way for politicians to lose elections.